The invention relates to a regulator and, more specifically to a regulator with a hysteresis-affected characteristic curve having a manually operable actuating element for presetting a desired control variable, an axially displaceable control slide for adjusting the preset control variable in accordance with its axial displacement and a control incline which is coupled to the actuating element and converts its adjustment movement into an axial displacement of the control slide. A control face of the control incline rises in the adjustment direction of the actuating element. The control slide rests in the axial direction with a spring force.
A pneumatic pressure regulator of this kind is disclosed in German Patent Document DE 3,144,247 Al. The manual actuating element is constructed as a manual selection wheel which, when rotated, axially displaces the control slide via the control incline coupled to said manual selection wheel. The control slide itself acts on a control spring constructed as a leaf spring and increases its initial stress with increasing axial displacement. The control spring, for its part, loads an axially displaceable control piston which rests against the valve closing element of a double-seated valve with an inner valve seat of said double-seated valve. When the valve seat is open, a connection exists between a control pressure chamber delimited by the control piston and a pressure-relief chamber which is blocked when the valve seat is closed. The valve closing element rests on a coaxial outer valve seat under the effect of a valve closing spring. The valve seat is arranged in a fixed manner and separates the control pressure chamber from a supply pressure chamber. The valve closing element is loaded in the closing direction by the pressure of a fluid, e.g. air, prevailing in the supply pressure chamber.
On the manual selection wheel there are marks which indicate the respectively set control pressure in the control pressure chamber and thus at the output of the pressure regulator. If the manual selection wheel is rotated to a mark which is numerically higher, the control slide is axially displaced, by means of the displacement of the control incline, towards the control spring, the initial stress of which is thus increased. The more strongly initially stressed control spring lifts off the valve closing element from the outer valve seat by means of the control piston, and a fluid short-circuit exists between the control pressure and high pressure chamber as a result of which the supply pressure increases. The valve closing element does not close the outer valve seat again until the sum of the supply pressure and valve closing spring forces acting on the valve closing element is greater than the difference of the control spring and control pressure forces acting on the control piston. The control pressure is thus set to the desired higher value.
When the manual selection wheel is set to a mark with a lower numerical value, the control incline is rotated in the inverse direction, as a result of which the control slide is displaced in the opposite displacement direction under the effect of the initially stressed control spring. The initial tension of the control spring decreases. The displacement force exerted by the control pressure on the control piston thus becomes greater than the oppositely directed force of the control spring, and the control piston lifts off with its inner valve seat from the valve closing element. As a result of the connection, thus released, to the pressure-relief chamber, the control pressure in the control pressure chamber drops until the force exerted by it on the control piston is smaller than the force of the control spring. The control piston then closes the valve seat and the lower control pressure is set at the output of the pressure regulator.
However, as a result of the hysteresis affecting the pressure regulator, the pressure regulator sets different control pressures with the same numerical setting on the manual selection wheel. This depends on whether the numerical setting is performed by rotating the manual selection wheel to the left or to the right. This can only be avoided if the numerical setting is always rotated from a single direction. If, for example, it is desired to set a higher control pressure, the manual selection wheel is initially set to a very much higher numerical value than the desired one and the desired numerical value is subsequently set. When selecting a lower control pressure, the lower numerical value is set directly. This manipulation is troublesome and not very user-friendly.
The present invention is based on improving a hysteresis-affected regulator of the above-mentioned type in such a way that, irrespective of the adjustment direction of the actuating element, the desired associated control variable is always set in a reproducible manner at the regulator output for all the settings of the actuating element.
This is achieved according to the present invention using a regulator having a hysteresis-affected characteristic curve which includes a manually operable actuating element for presetting a desired control variable, an axially displaceable control slide for adjusting the preset control variable in accordance with said control slide's axial displacement and, a control incline, having a control face, coupled to said actuating element for converting the actuating elements' adjustment movement into an axial displacement of the control slide. The control face rises in the adjustment direction of the actuating element. The control slide, via a spring force, rests in the axial direction. A toothing bears along the control face of the control incline. The toothing includes a multiplicity of equidistantly arranged teeth which have, in each case in two mutually perpendicular planes extending in the displacement direction of the control incline, a sawtooth-like contour in each case with one rising edge for running up the control slide and a falling edge which follows in the displacement direction, the rising edge of the one tooth contour falling away in the one displacement direction of the control incline and the rising edge of the other tooth contour falling away in the other displacement direction inversely to the latter rising edge of the control incline. The falling direction of the rising edge of the tooth contour, in the plane perpendicular to the control face of the control incline, coincides with the falling direction of the control face.
In the regulator according to the present invention, the control slide is initially displaced axially over-proportionally or super-proportionally by means of the specially formed toothing provided on the control face of the control incline. This occurs when the control incline is displaced in the direction of greater control variable setting, in order to subsequently cancel out the axial displacement again except for the required amount. Thus, in the hysteresis-affected characteristic curve of the regulator illustrated in FIG. 4, the characteristic curve is run through, for example, from point a to b via c to d in order to finally reach the desired final setting at e. The actuating element was adjusted in one direction, for example to the right from the position S.sub.1 to S.sub.2. On the other hand, when the control incline is displaced for the purpose of setting a smaller control variable, a proportional displacement of the control slide predetermined by the control face of the control incline occurs. The characteristic curve of which runs through according to FIG. 4 from point e to point a if, for example, the actuating element is reset from the setting S.sub.2 back to the setting S.sub.1, for example to the left.
This described process is unavoidably carried out in each case by the toothing depending on whether the actuating element is adjusted in one direction or the other and thus the control incline is displaced in one direction or oppositely in the other direction. When adjusting in the direction of a larger control variable, the control slide slides along the one tooth contour which lies in the plane extending in the displacement direction of the control incline at right angles to the control face. The over-proportional axial displacement of the control slide is effected when sliding along the rising edge and the partial reversal of this axial displacement of the control slide is effected when sliding along the falling edge. At the foot of the falling edge, the control slide assumes a kind of locking position from which it is pushed out again the next time the actuating element is actuated. When adjusting in the direction of a smaller control variable, the control slide slides along the control face and is laterally deflected by the other tooth contour so that it can bypass the tooth in order to assume a final position. The final position is again at the foot of the tooth where the falling edge of the one tooth contour and the rising edge of the other tooth contour come together. The setting of the control variable thus occurs in strictly predetermined intervals and not without increments. This is not detrimental to user-friendliness of the device.
The regulator according to the present invention can be used in many fields. For example, the regulator can be used as a fluid pressure regulator for seat contour adjustment in the case of orthopaedic vehicle upholstered seats or as an electrical potentiometer for compensating the hysteresis in the adjustment path of the potentiometer slide.
Advantageous embodiments of the regulator according to the invention with expedient further developments and embodiments of the invention are further described below.
According to a preferred embodiment of the invention, if the area of the control face of the control incline which extends along the rising edge of the tooth contour in the plane parallel to the control face is of a planar construction, in a deviation from the oblique course of the control face, it is ensured, by virtue of the spring force with which it is pressed on the control face, that the control slide is always automatically returned into one of the end positions between the teeth.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.